Type s fuse adapter



' Feb. 8, 1944. E. w. LANDMEIER 9 TYPE S FUSE ADAPTER Filed Jan. 9, 1942 1N VENTOR.

fiolwu'n WLanJmeiem BY Patented Feb. 8, 1944 TYPE s FUSE ADAPTER Edwin W-. Landmeier, Erlanger, Ky assignor to The Wadsworth Electric Manufacturing- Company, Covington, Ky., a corporation of Kentucky Application January 9, 1942, Serial No; 426,194

9 Claims.

The present invention relates to an improved fuse adapter whereby tamper-resisting circuit protective fuses known in the National Electric Code as type S fuses and of the type disclosed. in U. S. Patent No. 2,209,048, of July 23, 1940, are accommodated to the well known and widely used Edison base plug fuse holder.

An object of the invention is to provide a simplified fuse adapter structure; to eliminate parts of heretofore known plug fuse adapters without impairment of the tamper-resisting features of the circuit protective fuse installation; to ma terially reduce the cost of the adapters so that the use of tamper-resisting fuses may be widely adopted without hardship to users and thus correspondingly reduce the enormous losses in claim ages resulting from over-fusing of electric circuits and from lay-passing protective fuses with bridging materals inserted in the fuse receptacle.

A further object of the invention is to provide, in an adapter for tamper-resisting fuses of the class described, a positive and easily attained direct electrical connection between the center contacts of an Edison base fuse holder and the tamper-resisting ruse, respectively, and thus avoid a frequently experienced detrimental heating of fuses and blowing of fuses under loads below the rated amperage of the fuses.

A still further object of the invention is to provide a fuse adapter of this kind which affords access to the center contact screw of an Edison base plug fuse holder in which the adapter is mounted so that any necessary tightening of the said center screw may be effected even though the adapter be non-removably mounted in said fuse holder, and to avoid destruction and waste of the parts in the event a properly supervised change in the installation is required.

These and other objects are attained by the means described herein and described in the ac companying drawing, in which:

Fig. 1 is a vertical sectional view through a fuse block embodying an Edison base plug fuse holder, 2. tamper-resisting fuse and an adapter of the invention operatively accommodating the latter to the former.

Fig. 2 is an enlarged vertical sectional view of the fuse block of Fig. 1 with the fuse omitted and showing a modified form of the adapter of the invention.

The tamper-resisting fuses disclosed in U. S. Patent No. 2,209,048, of July 23, 1940, are designed so that a special fuse holder assembly may be required which will not accommodate a fuse of the same kind but of appreciably different-current-carrying capacity. This affords-good protection against the danger of overloaded circuits but is relatively expensive in practice from the standpoint of necessitating a variety of sizes of fuse holders to be stocked and from thestandpoint that many electrical devices such as fused. switch cabinets and branch circuit fuse cabinets canot be profitably assembled to an advanced state of completion for stock without limiting the use thereof to a designated load rating. The said Patent No. 2,209,648 provides for adapters that are non removably insertable in the well known Edison base fuse holders, but they, like the fuse holders of said patent, have an inherent disadvantage in that the fuses sometimes appear to be inserted tightly therein without attaining a fully effective connection between center contacts of the fuse and the holder or theadapter. The results of such inadvertence in seating the tamper-resisting fuse are the detrimental heating of the fuse and the blowing of the fuse below its rated capacity.

By the present invention the aforesaid disadvantage is obviated and at the same time the cost of manufacturing the adapter is reduced by such an amount as to favor a universal use of the well known Edison base plug fuse holders with the adapters of the invention both for existing installations and new constructions.

Referring now to Figure 1 of the drawing, the tamper-resisting fuse 8 is of the class described in the aforesaid U. S. Patent N0.-2,209,04=8 and available in the open markets where it is known as the type S or tamper-resisting fuse. It will be understood that the fuse 8 is subject to those variations contemplated by the patented disclosure for the purpose of preventing the insertion of a particular fuse of this type in an adapter that is specifically designed for a fuse of an appreciably. different rating. This is accomplished in part at least by the provision of threads of different pitch. on fuses of different ratings and the details thereof form no part of this invention; wherefore, further elaboration is unneces sary for the purposes of the present invention. The well known Edison base plug fuse holder 5 is suitably mounted on a fuse block I!) in any uitable manner as well known in the art. The adapter of the invention, indicated generally at lL-consists of a metal screw shell 12 externally threaded to fit the Edison base fuse holder 9 and provided with a means IQ, for example as shown in the aforementioned Patent No; 2,209,048, to preclude removal of the adapter after it has once been securely and tightly threaded into the fuse holder 9. Within the metallic shell I2 is a shell It of electric insulating material and a metal ring I5 of substantially the same diameter. Insulation I6 may be interposed between the periphery of ring I5 and shell I2. The upper end of shell I2 is turned inwardly over the top of ring I5 and it may be conveniently turned in a similar manner over the'remote end of insulating shell M.

It should be noted that when the adapter of the invention is driven home to the bottom of the Edison base plug fuse holder where it remains non-removable, the center contact I1 of said Edison base fuse holder projects into the hollow interior I8 of the adapter of the invention. The center contact I9 of the tamper-resisting fuse 8 may therefore be arranged to effect a positive and direct pressure abutment with the contact I! when the fuse 8 is screwed tightly enough into the adapter to bring the contact 20 of the fuse 8 into pressure abutment with the top, turned-over portion 2| of shell I2. The ring I5 has the serrated teeth and salient edge provided by an interruption of the thread thereon in the manner detailed in the aforesaid Patent No. 2,209,048 and which, together with the serrated disk 22 on the fuse, perform the function, as indicated in the patent, of making it difficult if not impossible to retain an inserted foreign bridging substance such as metal strips, foil or fine wires, without having the continuity thereof broken when the fuse is screwed firmly home into the adapter. The insertion of a metal disk in the bottom of the adapter for the purpose of bridging the fuse contacts is obviously ineffective because of the extent of insulating material between the top contact 2| of the adapter and the center contact I! of the Edison base fuse holder.

By the omission of any parts whatever in the bottom of the fuse holder, I am enabled to assure a firm positive contact directly between the center contacts of the Edison base fuse holder and the fuse within the interior of the adapter and there is thus avoided any likelihood of insufficient contact which experience has shown to occur not infrequently in installations of the aforenoted patented structure.

The adapters of the present invention will be understood to be externally uniformly adapted for non-removable insertion in Edison base plug fuse holders and they have been interiorly accommodated variously for the removable accommodation of fuses of specifically designated current-carrying capacities. Due to the simplification and reduced cost of manufacture of the adapters of the present invention, they may be economically made and installed in the Edison base fuse holders in various electrical devices at the time of specifically designating the duty of such apparatus, viz., at the time that the tamperresisting fuses are first applied.

Reference is now made to Figure 2 wherein parts identical with those in Figure 1 are designated by like reference numerals. In thi embodiment the internal shell of insulating material I40 may be a split shell divided vertically but nevertheless securely clamped by the crimping or turning over of the ends of metal screw shells I2. The separation of the parts along lines such as 23 at opposite sides of a diameter facilitates the assembly in manufacture of the adapters and also permits of numerous variations in the threads, including staggering of threads if desired to render certain adapters useful only with correspondingly threaded tamper-resisting fuses and thus further reduce the chances of improperly fusing a given installation. The serrations 24 on the thread of ring I5 are illustrated in Figure 2 and will be understood to be essentially like those of the aforesaid patented structure. In the modified form in Figure 2 a bottom insulating Washer 25 having an inside diameter which fully clears the center contact I! of the Edison base plug fuse holder may be utilized. A thin sheet metal threaded ring 2% may be provided interiorly within the bottom end of the insulating shell IN to cooperate with the serrated disk 22 at the lower end of the fuse 8 if desired. Such an arrangement offers no material benefit to an effort to insert a bridge of foreign conductor material between contacts IT and 2!. This sheet metal threaded ring 25 likewise affords no advantage in the "use of an inserted bridging disk such as a penny in view of the relatively greater number of threads of insulating material on the insulating shell Mi! and the fuse 8.

From the foregoing it should be readily apparent that an economical structure of improved effectiveness has been provided.

What is claimed is:

1. A fuse adapter of the class described consisting of an outer metal screw shell, an inner screw shell of electric insulating material, and an inner metal ring at the end of the last mentioned shell, together forming an internally threaded tube contained within and axially coextensive with the metal shell and adapted for the reception of a type S fuse, said metal shell adapted for non-removable mounting in an Edison base plug fuse holder to a depth such that the central contact of the said holder may make unobstructed direct abutting contact interiorly of the adapter with the central contact of a fuse inserted in said adapter.

2. A fuse adapter of the class described consisting of a composite metal and insulation shell of hollow interiorly unobstructed tubular form, the exterior portion being of metal and arranged for non-removable mounting in an Edison base plug fuse holder, the interior portion including a threaded section of electric insulating material, and a narrow internally threaded metal ring for reception of a tamper-resisting fuse permitting positive abutment within the shell of the respective center contacts of an Edison base plug fuse holder and a tamper-resisting fuse, the interior of said adapter arranged for cooperation with an inserted fuse to break the continuity of a foreign electric conductor positioned to bridge the fuse within said holder and adapter.

3. As a new article of manufacture, an adapter for accommodating a tamper-resisting fuse to an Edison base fuse holder and comprising a composite shell of metal and electric insulating material having an unobstructed axial bore of substantially uniform diameter completely through it.

4. A fuse adapter for accommodating a tamper-resisting fuse to an Edison base plug fuse holder consisting of an externally threaded metal shell adapted for non-removable insertion in such Edison base fuse holder, and interiorly open uniformly and unobstructed from end to end for receiving the center contacts of such holder and an inserted tamper resisting fuse in positive abutment with each other within the adapter.

5. The combination with an insulating support of an Edison base plug fuse holder mounted thereon, a type S fuse, and an adapter non-removably mounted in the fuse holder and having a uniform and unobstructed bore completely therethrough affording free and uninterrupted passage for the threaded insertion of said fuse with the center contact thereof in positive electrical contact with the center contact of said fuse holder interiorly of said passage in said adapter, the interior of the adapter arranged for cooperation with an inserted fuse to break the continuity of a foreign electrical conductor inserted within said adapter and fuse.

6. An adapter of the class described comprising an internally threaded shell of insulating material, a metal ring at the end thereof having a serrated and interrupted thread thereon. and an exterior metal threaded shell embracing the side wall and ends of said insulating shell and ring, the threaded interior of said adapter having a uniform and unobstructed opening therethrough from end to end.

7. A fuse adapter of the class described consisting of an outer metal screw shell, an inner screw shell of electric insulating material, and an inner metal ring at the end of the last mentioned shell, together forming an internally uniform and unobstructed threaded tube contained within and axially coextensive with the metal shell and adapted for the reception of a type S fuse, said metal shell adapted for mounting in an Edison base plug fuse holder to a depth such that the central contact of the said holder may enter the adapter from one end thereof and make unobstructed direct abutting contact with the central contact of a fuse inserted in the other end of said adapter.

8. A fuse adapter of the class described consisting of a composite metal and insulation shell of hollow tubular form, the exterior portion being of metal and arranged for mounting in an Edison base plug fuse holder, the interior portic-n including an end to end uniformly open and unobstructed threaded section of electric insulating material, and a narrow internally threaded metal ring for reception of a tamperresisting fuse permitting positive abutment within the shell of the respective center contacts of an Edison base plug fuse holder and a tamperresisting fuse, the interior of said adapter arranged for cooperation with an inserted fuse to break the continuity of a foreign electric conductor positioned to bridge the fuse within said holder and adapter.

9. A fuse adapter for accommodating a tamper-resisting fuse to an Edison base plug fuse holder consisting of an externally threaded metal shell adapted for insertion in such Edison base fuse holder, and interiorly open uniformly and unobstructed from end to end for receiving the center contacts of such holder and an inserted tamper-resisting fuse in positive abutment with each other within the adapter.

EDWIN W. LANDMEIER. 

